Effect of phosphonoformic acid, dietary phosphate and the Hyp mutation on kinetically distinct phosphate transport processes in mouse kidney.
Biochim Biophys Acta
; 984(2): 207-13, 1989 Sep 04.
Article
en En
| MEDLINE
| ID: mdl-2527564
We examined the kinetics of phosphate transport in mouse renal brush-border membrane vesicles under initial rate (6 s), trans zero, voltage clamp conditions. Two kinetically distinct Na+-dependent phosphate transport processes were identified: a high-affinity, low-capacity system (Km, 0.09 +/- 0.02 mM; Vmax, 539 +/- 50 pmol/mg protein per 6 s) and a low-affinity, high-capacity system (Km, 1.28 +/- 0.35 mM; Vmax, 1677 +/- 198 pmol/mg protein per 6 s). The high-affinity system was inhibited competitively by 1 mM phosphonoformic acid (PFA) (apparent Ki, 0.31 +/- 0.03 mM) and completely abolished by 20 mM PFA; the low-affinity system was insensitive to 1 mM PFA and was inhibited competitively by 20 mM PFA (apparent Ki, 9.03 +/- 1.21 mM). Dietary phosphate deprivation elicited a significant increase in Vmax of both high- and low-affinity phosphate transport systems whereas the X-linked Hyp mutation caused a 50% decrease in Vmax of the high-affinity system with no change in the low-affinity system. Phosphate deprivation of Hyp mice elicited a 3.5-fold increase in Vmax of the high-affinity system. Neither diet nor mutation significantly altered the apparent Km values of either phosphate transport process. We conclude that (1) mouse kidney brush-border membranes have two distinct Na+-dependent phosphate transport systems which differ in affinity and capacity; (2) both processes participate in the adaptive response to dietary phosphate restriction; (3) only the high-affinity system is impaired by the X-linked Hyp mutation.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Compuestos Organofosforados
/
Fosfatos
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Ácido Fosfonoacético
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Riñón
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Microvellosidades
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Mutación
Límite:
Animals
Idioma:
En
Revista:
Biochim Biophys Acta
Año:
1989
Tipo del documento:
Article
País de afiliación:
Canadá
Pais de publicación:
Países Bajos